(1) One largish (orange) pumpkin
(1) One sturdy spoon
(1) Sharp knife .
(1) Small source of light, such as a candle.

Though there are probably many ways to carve a pumpkin, this is how I've usually seen it done:

First, cut a circular hole in the top of the pumpkin, around the stem. Make sure the hole narrows downward, so you can put this plug back in later. It looks nicer that way. Remove the top off your pumpkin

Then, the messy part: Emptying the pumpkin. When you lift up the plug you, you should see a nasty mess of orange bits, with seeds in them. Take your spoon (or scraping instrument of choice), and proceed to scrape the inside walls of the pumpkin free of all the gunk. Some people like to eat the pumpkin seeds, and maybe even other bits. When all the gunk is out, and the walls are nice and smooth, proceed to the next step.

The carving of the actual figure on the pumpkin is an artform that people can spend hours on. First, one must come up with a clever design: One that is attractive, but still something everyone will recognize. Trying to carve the head of Abraham Lincoln, for example, will probably not work, for example, unless you're really good at this.

One can buy pumpkin pattern books from stores; these patterns can get very complicated, but if properly executed, will look great.

Typically, one first draws the outline of the carving onto the pumpkin before starting. The knife used should be sharp, long, and narrow, to allow one to cut through the inch or two of pumpkin, but still be able to cut detailed shapes into the pumpkin.

In the end, place the light source, like a candle, into the center of the pumpkin, and light it. This should illuminate the carving from the inside, ready for night-time display. Enjoy!